1. Field of the Invention
The present invention relates to an electron beam exposure method and apparatus and an exposure control data construction method and, more particularly, to an electron beam exposure method and apparatus for drawing partial patterns on a plurality of element exposure regions, arranged two-dimensionally on a substrate, with a plurality of electron beams, thereby drawing one pattern on the substrate, and a method of constructing exposure control data necessary for controlling this apparatus.
For example, the method and apparatus according to the present invention can be suitably used for drawing a pattern on a substrate such as a silicon wafer or glass substrate, or for drawing a pattern on a material for forming a mask or reticle in order to form the mask or reticle.
2. Description of the Related Art
FIG. 15A shows the outline of a conventional multi electron beam exposure apparatus. Reference numerals 501a, 501b, and 501c denote electron guns; 502, a reduction electron optical system; and 504, a deflector. The electron guns 501a, 501b, and 501c can turn on/off electron beams separately. The reduction electron optical system 502 reduces a plurality of electron beams emitted by the electron guns 501a, 501b, and 501c and projects the reduced electron beams onto a wafer 503. The deflector 504 deflects the plurality of reduced, projected electron beams onto the wafer 503.
The plurality of electron beams emitted by the electron guns 501a, 501b, and 501c are deflected by the deflector 504 with the same deflection amount. The respective electron beams are thus deflected, with reference to their beam reference positions, while their positions on the wafer are sequentially settled in accordance with the arrangement having array gaps determined by the minimum deflection width of the deflector 504. The respective electron beams expose different element exposure regions with patterns to be exposed.
FIGS. 15A, 15B, and 15C show how the electron beams from the electron guns 501a, 501b, and 501c expose patterns, that should be exposed, onto corresponding element exposure regions (EF1, EF2, and EF3) in accordance with the same arrangement. The respective electron beams move while their positions are settled such that their positions on the respective arrays at the same time point become (1,1), (1,2), . . . , (1,16), (2,1), (2,2), . . . , (2,16), (3,1), . . . The electron beams actually irradiate the wafer 503 at positions where the patterns (P1, P2, and P3) to be exposed exist, thereby exposing the respective element exposure regions with the patterns to be exposed.
When drawing a pattern with the electron beam exposure apparatus, electrons incoming to the wafer are reflected and scattered by the wafer (backscattering). The scattered electrons photosensitize portions of a resist applied to the wafer excluding incident points. This is a phenomenon called a proximity effect. Due to the proximity effect, the resist pattern after development has a shape and size different from the desired shape and size.
In a variable shaping type electron beam exposure apparatus, a pattern to be drawn is divided into a plurality of regions in order to reduce the proximity effect, and the irradiation amount is adjusted in units of regions.
In the conventional multi electron beam exposure apparatus, the irradiation time is fixed so that all of the plurality of electron beams have the same irradiation amounts at the irradiation positions. Therefore, data necessary for controlling irradiation of the respective electron beams is sufficient if it is 1-bit data representing whether to irradiate the electron beam. When, however, the irradiation amounts of the electron beams are adjusted in units of appropriate regions in order to reduce the proximity effect, in the multi electron beam exposure apparatus, the electron beam irradiation time must be adjusted in units of irradiation positions of the respective electron beams. For example, as data necessary for controlling irradiation time having 128 gradation levels, 7-bit data are added to the control data of each irradiation cycle of the electron beams, thus multiplying the exposure control data by 8. In other words, when reducing the proximity effect, in the multi electron beam exposure apparatus, the data amount increases very much.
The present invention has been made in view of the above situation, and has as its object to determine the electron beam irradiation amount of one irradiation cycle in units of element exposure regions, thereby decreasing the amount of data necessary for controlling exposure operation.
According to the first aspect of the present invention, there is provided an electron beam exposure method of drawing partial patterns on a plurality of element exposure regions, two-dimensionally aligned on a substrate, with a plurality of electron beams, thereby drawing one pattern on the substrate, comprising the determination step of determining an electron beam irradiation amount of one irradiation cycle for each element exposure region by considering a pattern to be drawn on a predetermined region including the element exposure region, and the drawing step of drawing the partial patterns on the element exposure regions on the substrate with the electron beams while controlling an irradiation amount of each electron beam in accordance with the electron beam irradiation amount of one irradiation cycle determined for each of the element exposure regions in the determination step, thereby drawing one pattern on the substrate.
In the electron beam exposure method according to the first aspect of the present invention, the element exposure regions are preferably aligned with an array pitch not more than a backscattering diameter of the electron beams.
In the electron beam exposure method according to the first aspect of the present invention, the electron beams are preferably aligned on the substrate with a gap not more than a backscattering diameter of the electron beams.
In the electron beam exposure method according to the first aspect of the present invention, the determination step preferably comprises determining the electron beam irradiation amount of one irradiation cycle for each element exposure region by considering a count with which the electron beam irradiate the predetermined region including the element exposure region.
In the electron beam exposure method according to the first aspect of the present invention, the determination step preferably comprises determining the electron beam irradiation amount of one irradiation cycle for each element exposure region by considering an area density of the pattern to be drawn within the predetermined region including the element exposure region.
In the electron beam exposure method according to the first aspect of the present invention, the determination step preferably comprises determining the electron beam irradiation amount of one irradiation cycle for each element exposure region by considering a barycentric position of the pattern to be drawn within the predetermined region including the element exposure region.
In the electron beam exposure method according to the first aspect of the present invention, the determination step preferably comprises determining the electron beam irradiation amount of one irradiation cycle for each element exposure region by considering a position to be irradiated with the electron beam within the predetermined region including the element exposure region.
In the electron beam exposure method according to the first aspect of the present invention, the method preferably further comprises the acquisition step of acquiring the pattern to be drawn on the substrate, and the division step of dividing the pattern acquired in the acquisition step into units of element exposure regions, and the determination step preferably comprises determining the electron beam irradiation amount of one irradiation cycle for each element exposure region on the basis of the pattern divided in the division step.
According to the second aspect of the present invention, there is provided a method of constructing exposure control data for controlling a process of drawing one pattern on a substrate by drawing partial patterns on a plurality of element exposure regions, two-dimensionally aligned on the substrate, with a plurality of electron beams, comprising the acquisition step of acquiring the pattern to be drawn onto the substrate, the division step of dividing the pattern acquired in the acquisition step into units of element exposure regions, the determination step of determining an electron beam irradiation amount of one irradiation cycle for each element exposure region by considering the pattern to be drawn on a predetermined region including the element exposure region, and the construction step of constructing the exposure control data on the basis of a determination result of the determination step and recording the exposure control data on a memory medium.
According to the third aspect of the present invention, there is provided a computer-readable program, for constructing exposure control data for controlling a process of drawing one pattern on a substrate by drawing partial patterns on a plurality of element exposure regions, two-dimensionally aligned on the substrate, with a plurality of electron beams, comprising the acquisition step of acquiring the pattern to be drawn onto the substrate, the division step of dividing the pattern acquired in the acquisition step into units of element exposure regions, the determination step of determining an electron beam irradiation amount of one irradiation cycle for each element exposure region by considering the pattern to be drawn on a predetermined region including the element exposure region, and the construction step of constructing the exposure control data on the basis of a determination result of the determination step and recording the exposure control data on a memory medium.
According to the fourth aspect of the present invention, there is provided an electron beam exposure apparatus for drawing partial patterns on a plurality of element exposure regions, two-dimensionally aligned on a substrate, with a plurality of electron beams, thereby drawing one pattern on the substrate, comprising determination means for determining an electron beam irradiation amount of one irradiation cycle for each element exposure region by considering a pattern to be drawn on a predetermined region including the element exposure region, and drawing means for drawing the partial patterns on the element exposure regions on the substrate with the electron beams while controlling an irradiation amount of each electron beam in accordance with the electron beam irradiation amount of one irradiation cycle determined for each of the element exposure regions by the determination means, thereby drawing one pattern on the substrate.
Further objects, features and advantages of the present invention will become apparent from the following detailed description of an embodiment of the present invention with reference to the accompanying drawings.